The XECryption Solver GUI program is designed to assist you in deciphering text encrypted by the XECryption cipher. This cipher appears to originate from the realistic mission level 6 on hackthissite.org. In addition to the binary you can also download the source code which is licensed under the GPL version 2.0. The program is written in C# and so you probably need one of those .NET framework things installed.

Here you can download the report (Norwegian) and the implementation (C# source code) of the RSA encryption algorithm Jens Otto Hatlevold and I did. It was done in 2006 for a project in the computer security course at the University of Stavanger. You can view the source code repository online with FishEye.